For many slow readers, placing and holding a pencil lengthwise in between the lips makes a significant difference. In early reading training, people are taught to read aloud. As they grow older and begin to read silently, the habit of moving the lips stays with them. This limits their reading speed to what they can read aloud. By forcing the lips to remain still, the brain can begin to read faster. After a few weeks of practice, you can remove the pencil while reading.
The "finger down the middle of the page" teaches a reader to use their entire vision to capture a whole sentence with one glance instead of reading one word at a time. Start with easier-to-read children's books at about the third-grade level.
Place your index finger in the center of the first line on the page and slowly move it downward while trying to capture the whole line of print just above the finger with your vision. Concentrate on seeing all the words on that line at once and understanding them. Don't worry about speed. As you begin to capture whole lines, pick up the speed. As your speed begins to get faster, continue the exercise with harder-to-read books.
A hard habit to break is unnecessarily allowing your eyes to wander back to something that has already been read and rereading it. This brings reading speed to an almost total stop if done enough times. Use an index card to cover each line as you read it, starting from the top of the page. Even if you feel you missed something, continue on with the reading and resist the temptation to remove the card to check.
Again, this works best if started with easier books until the new habits become ingrained.
Understanding how deeply a text should be read can speed up reading considerably. Some reading, such as for schoolwork, might need to be read slower and with more comprehension. Going back and rereading a paragraph or two may be in the reader's best interest. Other material, such a the summer novel at the beach, can be read with more of a "skimming" type of interest, with words, paragraphs and sometimes even whole pages just merely looked at to see if they are of any interest.